Pharmacokinetic Analysis and Biomarker-Assisted Safety Assessment of Acetaminophen in Combination With Ojeok-san Compared With Acetaminophen Alone

Acetaminophen and Ojeok-san are both frequently used analgesics. In this study, we evaluated acetaminophen pharmacokinetics (PK) and changes in microRNA-122 (miR-122) levels after multiple dosing of acetaminophen with or without Ojeok-san. An open-label, 1-sequence, 2-period, 2-treatment crossover study was conducted in 18 subjects. In period 1, 500 mg of acetaminophen was administered 3 times on day 1 and once on day 2. In period 2, after the administration of 14.47 g of Ojeok-san twice on day 2 and 3 times daily on days 3 to 7, Ojeok-san and acetaminophen were coadministered 3 times each on day 8 and once each on day 9. The geometric mean ratios (90% confidence intervals) of acetaminophen with Ojeok-san to acetaminophen alone were 0.98 (0.87 to 1.10) and 1.02 (0.98 to 1.05) for the maximum plasma concentration (C_max) and the area under the plasma concentration-time curve during the dosing interval (AUC_0-τ), respectively, of acetaminophen at steady state. The alanine aminotransferase (ALT) levels were within the reference range in all the participants throughout the study period, although the mean fold changes in both serum miR-122 and ALT levels from baseline tended to increase on days 2 to 5. In conclusion, the PK properties of acetaminophen were not significantly affected by Ojeok-san coadministration. For osteoarthritis patients taking acetaminophen with or without Ojeok-san, monitoring potential liver toxicity using miR-122 as a biomarker may be useful.